3.4 I/O Status Block

The I/O status block (IOSB) for QIO functions on magnetic tape devices is shown in Figure 3-6. Appendix A lists the status returns for these functions. (The OpenVMS system messages documentation provides explanations and suggested user actions for these returns.) Table 3-2 (in “Magnetic Tape Driver Device Information”) lists the device-dependent data returned in the second longword. The IO$_SENSEMODE function can be used to return that data.

Figure 3-6 IOSB Contents

The byte count is the actual number of bytes transferred to or from the process buffer or the number of files or blocks skipped. (If an IO$_SKIPRECORD function is terminated by the detection of a tape mark, the count returned in the IOSB is an unsigned number reflecting the number of blocks skipped, plus 1.